Querying

Mix.install([:ash])

Querying

In this tutorial you will do basic Query and CRUD operations

But first you need to enable all basic CRUD operations.

Do this by adding the :read, :update and :destroy action to your actions.

Show Solution

  defmodule Tutorial.Profile do
    use Ash.Resource,
      data_layer: Ash.DataLayer.Ets

    actions do
      defaults [:create, :read, :update, :destroy]
    end

    attributes do
      uuid_primary_key :id
      attribute :name, :string
    end
  end

  defmodule Tutorial do
    use Ash.Api

    resources do
      resource Tutorial.Profile
    end
  end

Enter your solution

defmodule Tutorial.Profile do
  use Ash.Resource,
    data_layer: Ash.DataLayer.Ets

  actions do
    defaults([:create])
  end

  attributes do
    uuid_primary_key(:id)
    attribute(:name, :string)
  end
end

defmodule Tutorial do
  use Ash.Api

  resources do
    resource(Tutorial.Profile)
  end
end

Creating

Add 2 Profiles to the database.

• One with the name “Joe Armstrong”
• One with your name

You can create a Profile by:

• Creating a Changeset with Ash.Changeset.for_create(Tutorial.Profile, :create, %{name: "Your Name"}),
• Then giving the changeset to Tutorial.create!().

Hint: Use a pipeline

Show Solution

  Tutorial.Profile
  |> Ash.Changeset.for_create(:create, %{name: "The Name"})
  |> Tutorial.create!()

Enter your solution

Reading

Now, read all the generated Profiles.

Call Tutorial.read!/1 with the Tutorial.Profile module.

Show Solution

  Tutorial.Profile
  |> Tutorial.read!()

Enter your solution

Now fetch the “Joe Armstrong” Profile.

You can achieve this by introducing a filter.

First you’ll need to require Ash.Query

Then call Ash.Query.filter(name == "Joe Armstrong") with the Tutorial.Profile.

Put the result into the joe variable. read!/1 returns a list, so make sure to extract the single returned value out of that list.

Show Solution

  require Ash.Query

  [joe] = 
    Tutorial.Profile
    |> Ash.Query.filter(name == "Joe Armstrong")
    |> Tutorial.read!()

Enter your solution

You’ll use the joe variable in the next sections.

Updating

Now change Joe Armstrong‘s name to Neil Armstrong.

You can do this by providing the Ash.Changeset.for_update/3 with:

• the resource you want to change, in this case joe
• the :update atom
• a map of the values you want to change, in this case %{name: "Neil Armstrong"}

Then apply the changeset by calling Tutorial.update!/1 with the changeset.

Hint: Using a pipeline might be a good idea.

Show Solution

  joe
  |> Ash.Changeset.for_update(:update, %{name: "Neil Armstrong"})
  |> Tutorial.update!()

Enter your solution

Destroying

Finally, remove joe from the database.

Do this using the Tutorial.destroy!/1 function.

Show Solution

  Tutorial.destroy!(joe)

Enter your solution